Abstract
Almost 25% of all older adults experience difficulty walking. Mobility difficulties for older adults are more pronounced when they perform a simultaneous cognitive task while walking (i.e., dual task walking). Although it is known that aging results in widespread brain atrophy, few studies have integrated across more than one neuroimaging modality to comprehensively examine the structural neural correlates that may underlie dual task walking in older age. We collected spatiotemporal gait data during single and dual task walking for 37 young (18–34 years) and 23 older adults (66–86 years). We also collected T1-weighted and diffusion-weighted MRI scans to determine how brain structure differs in older age and relates to dual task walking. We addressed two aims: (1) to characterize age differences in brain structure across a range of metrics including volumetric, surface, and white matter microstructure; and (2) to test for age group differences in the relationship between brain structure and the dual task cost (DTcost) of gait speed and variability. Key findings included widespread brain atrophy for the older adults, with the most pronounced age differences in brain regions related to sensorimotor processing. We also found multiple associations between regional brain atrophy and greater DTcost of gait speed and variability for the older adults. The older adults showed a relationship of both thinner temporal cortex and shallower sulcal depth in the frontal, sensorimotor, and parietal cortices with greater DTcost of gait. Additionally, the older adults showed a relationship of ventricular volume and superior longitudinal fasciculus free-water corrected axial and radial diffusivity with greater DTcost of gait. These relationships were not present for the young adults. Stepwise multiple regression found sulcal depth in the left precentral gyrus, axial diffusivity in the superior longitudinal fasciculus, and sex to best predict DTcost of gait speed, and cortical thickness in the superior temporal gyrus to best predict DTcost of gait variability for older adults. These results contribute to scientific understanding of how individual variations in brain structure are associated with mobility function in aging. This has implications for uncovering mechanisms of brain aging and for identifying target regions for mobility interventions for aging populations.
Highlights
Dual task walking performance is more predictive of falls in aging than single task walking performance (Ayers et al, 2014; Johansson et al, 2016; Verghese et al, 2017; Halliday et al, 2018; Gillain et al, 2019)
We identified widespread brain atrophy for older adults; across imaging modalities, we found the most prominent age-related atrophy in brain regions related to sensorimotor processing
In this multimodal neuroimaging study, we found widespread age-related atrophy across cortical, subcortical, and cerebellar regions, but in regions related to sensorimotor processing
Summary
25 percent of older adults report serious mobility problems such as difficulty walking or climbing stairs (Kraus, 2016). Older adults tend to encounter even greater difficulty with performing a secondary cognitive task while walking, i.e., dual task walking (e.g., Springer et al, 2006; Hollman et al, 2007; Malcolm et al, 2015; Smith et al, 2016). Dual task walking performance is more predictive of falls in aging than single task walking performance (Ayers et al, 2014; Johansson et al, 2016; Verghese et al, 2017; Halliday et al, 2018; Gillain et al, 2019). This could be because dual task walking provides a better analog for real-world scenarios. Given the link between dual task walking performance and falls, and its greater ecological validity, we selected to analyze dual instead of single task walking
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